#!/usr/bin/perl

# Unicode entity text => Unicode decimal number
%lookup = ("Adieresis" => 196,
           "Aring" => 197,
           "Ccedilla" => 199,
           "Eacute" => 201,
           "Ntilde" => 209,
           "Odieresis" => 214
          );

# A few lines of text to test.
# Only elements 4 and 6 should match
@source = ("fred",
           "adieresis",
           "Adieresis",
           "&adieresis;",
           "&Adieresis;",
           "",
           "fr&Adieresis;ed"
);

foreach (@source) {
  # regexp: [^;]+? matches 1+ characters which are not a semi-colon
  #        ([^;]+?) Remember it (in $1)
  #       &([^;]+?);? basically matches a (pseudo) entity
  s/&([^;]+);?/"&#".eval(exists $lookup{\1} ? $lookup{\1} : \1).";"/e;
  print "($1) $_\n";
}

##</code><code>##

() fred
() adieresis
() Adieresis
(adieresis) &#;
(Adieresis) &#;
(Adieresis) 
(Adieresis) fr&#;ed